To a scientific outlook, this can look like a
straightforward and obvious statement of fact.
Given that minds are real (we hope this much
is apparent, even to hard-line materialists)
and that if we look with our scientific
instruments we find only
physical stuff, it
is convenient and simple to identify the mind
with the physical stuff that we find when we
go looking for it scientifically.

But this view does not mesh straightforwardly
with our commonsense notions and our
normal linguistic practices,
hence the identity theory has been the subject
of much controversy. Nonetheless, it has been
extremely influential, and most current
discourse in analytic philosophy on the
ontology of the mental has been shaped by its
defence, development or opposition.

In the ancient world, Epicurus could
be considered a kind of identity theorist, but
in its modern formulation, the originators of
the theory were Herbert Feigl1,
J.J.C. Smart and U.T. Place.

Place took the view that phenomena such as
after-images, though real, can't be
accounted for in a dispositional (ie.behaviourist) analysis of the mental (which
he favoured in the case
of concepts like belief and intention.)
Finding untenable the traditional dualist
view of mental events as distinct from, though
correlated with, physical events, he
was led to postulate the identity of
the former with the latter. His view was
that this identification was a scientific theory,
in the same way that the identification of lightning
with the motion of electrical particles is
not a necessary truth, but a contingent one that
we establish empirically.

The theory was expanded by D.M. Armstrong in
his influential book A Materialist Theory
of Mind where it was elevated to a fully
fledged ontology. Roughly, Armstrong's view
is that all real properties are causally based;
he called this the causal theory of properties
or CTP for short.

Thus, if we want to say that 'mental properties'
(like is seeing a red after-image, for example)
are real, then unless we wish to invent some
non-physical variety of causality, which Armstrong
certainly did not want to do, we have to
postulate some corresponding physical property
of the brain, in virtue of which our claim to
be seeing a red after-image can be thought true.

But, as was pointed out, we need to be clear
whether we are identifying mental
properties with physical ones or just individual
mental events and states with physical ones.

A theory which supports the view that mental
properties are real and identical with physical
ones is called a type-type identity theory,
as it asserts there are types of mental events
which are identical with types of physical events.

The more hard-linetoken-token identity
theory, by contrast, is one in which we assert
the identity of particular, single, mental
states and events with particular single physical
ones, but deny that there are necessarily any
real physical properties corresponding to the
terms we use to classify the mental (terms such
as after-image, for example.)

The type-type theories, then, are realist about
our descriptions of the mental (or at least they
allow realism about these) whereas the token-token
theories are not: propositions about
the mental can be seen, at best, as useful
approximations to the true physical description,
or as simply denoting arbitrary disjunctions
of physical objects.
This has obviously travelled some distance from
the identity theory as originally conceived, which
sought to preserve the potential truthfulness of
statements about the mental, and the token-token theory
has been criticised for simply restating
epiphenomenalism - the theory that mental
events are some strange metaphysical exudence
of physical ones - in a hidden guise.

But if, adopting the type-type approach, we say an after-image is identical to a process in the brain, then since the after-image is green we would have to say that the brain-process is green, since identicals share all properties. This objection against the type-type theories is regarded by many as fatal.

Donald Davidson has put forward a theory
known as anomalous monism in which, though
only token-token identity holds between the mental
and the physical, there are nonetheless real
physical and mental properties, but with no
type-type-like correlation between them.

My own view is that it's the materialist, or
physicalist stance that's leading us
into trouble here. I am not inclined to say that
there are two of me here, a physical one and a
mental one, but if we adopt Armstrong's
CTP, together with his view (shared, I think,
by most identity theorists) that 'causal'
means 'investigable by physics', then it seems
quite clear that descriptions that are acceptable
in physics will not exhaustively describe
our experience (see inverse spectrum argument.)
So I am led to postulate a
'dual aspect' version
of neutral monism, instead.

The most significant current objection to
the identity theory, however, is widely thought to be
Hilary Putnam's multiple realizability
argument, which considers that it would be
possible for many different physical states to implement
a single mental state, and since the mental
states are identical to each other and the
physical ones not, the mental states can't be
identical with the physical ones. This consideration
has probably been influential for those
who espouse computationalist
theories of mind on the analogy that many different physical
arrangements can realise identical computations.

The concept of the mind has appeared as a powerful idea that has inspired lively debate among philosophers, psychologists, doctors and even physicists. While this debate has been interesting, none of these groups have reached a consensus on exactly what the mind should be defined as. Thus, for the purposes of this essay, I have chosen to define the mind as the sum of all of the conscious and subconscious mental activity in the forms of internal images, sounds, feelings, smells and tastes that make up an individuals subjective experience of the world. I have chosen this definition for several reasons. The word “mind” itself belongs to a class of nouns termed nominalizations, which are nouns that in fact describe a process rather than a static thing. The definition I have provided avoids this Aristotelian “thingness” about the mind and allows us more precise discussion. Second, I believe this definition avoids placing the concept of “mind” into any particular school of thought that may bias the discussion. Given this definition of mind, I propose that it can be neither proven nor disproven that the mind is embedded in the brain. For the purpose of this discussion, "Is the mind embedded in the brain?", I will take that to mean that the existence of mind is dependent upon the brain, and that the mind is localized within the brain.

Neuroscience tells us that the brain transduces energy from the outside world into neural impulses. At first, this appears to explain some of the above questions, however upon closer examination we are left with more questions than answers. Neuroscience provides a very complex and detailed picture of the structure of the process of sensing, but fails to address the content. We know, for example, that red light has a particular structure in terms of its wavelength and its effect on certain types of neurons: this is the structure. What we do not know and can not prove is whether my subjective experience of red (qualia) corresponds objectively with someone else’s experience of red: our subjective experience of red is the content, and falls under my definition of mind. Could it be then that the brain provides the structure, while the mind provides the content? If so, then the concept of mind is inherently untestable scientifically, however this may merely be a problem in the definition. The study of the transduction of sound waves into neural impulses reveals another mystery. Certain frequencies of sounds are detected by certain neurons that fire in response to the sound. Other sound frequencies are detected by the rate that the neurons fire. This information is transmitted to the auditory cortex, but how do those impulses get translated into my experience of a symphony? And how might my experience of a symphony differ from somebody else with essentially the same brain structure? How is the information in the neuron decoded into my experience and integrated with the rest of my ongoing experience?

This brings me to my next point. If the mind is not embedded in the brain, then how does the administration of drugs that act on the brain appear to affect the mind? This issue can be resolved in several ways and still remain consistent with my thesis. If the mind is non-local as I discussed earlier, then the apparent effects of drugs on the mind can be explained by the drug’s effect on the mechanism by which the mind manifests itself through the brain. A useful analogy here would be to consider a dam built on a river where the water is the mind and the river valley is the brain. When the dam is built, it changes the structure of the river valley, and interferes with the movement of the water. Another way to approach this issue is again the structure vs. content. Drugs change the physical structure of the operation of the brain and neurotransmitters, if only temporarily. This can be fairly easily predicted in most cases. The content of the drug experience, however, can only be put into generalizedcategories. When a person ingests LSD we know that they will have some sort of sensory distortions, yet we cannot predict precisely what those sensory distortions will be or what specific things they may hallucinate. Again, this is a difference in structure and content that I find relevant.

One very interesting thing is that the number of neurons containing sense information going forward in the brain is only one-tenth the number of neurons pointing in the other direction. This also ties in with the visual blind spot that we rarely notice. This is just some of the evidence that our experience of the world is a creative process.

I am ending this essay with more questions that I had when I started. The only thing I can be reasonably certain about is that whether the mind is embedded in the brain or not probably depends on your definition of mind. I don’t think this question will be easily resolved until further advances are made in brain research, quantum mechanics (local vs. non-local phenomenon), and a consensus on a scientifically testable concept of mind is reached.